Austenitic stainless steel with extra low nitrogen and boron content to mitigate irradiation-assisted stress corrosion cracking

摘要

The present invention relates to a stainless steel alloy composition having resistance to irradiation promoted stress corrosion cracking and containing a low nitrogen content with a maximum of 0.01 wt-% being readily achievable. Substantially all of the nitrogen should be located in the alloy matrix and not in the grain boundaries. This is preferably achieved by "trapping" nitrogen in the matrix before it has a chance to segregate to the grain boundaries during irradiation. The alloy composition also should contain as low a boron content as possible with a maximum of 0.003 wt-% being readily achievable. Substantially all of the boron is located in the alloy matrix and not in the grain boundaries and boron is also "trapped", in order to achieve the desired location. The alloy composition also contains a maximum of 0.01 wt-% carbon provided that the strength requirements of the composition still can be met. The silicon, phosphorous, and sulfur content combined should be as low as possible. Preferably, silicon is restricted to a maximum of 0.02 wt-% while phosphorous and sulfur are each restricted to a maximum content of about 0.002 wt-%. The nickel content of the stainless steel alloy composition ranges generally between about 9 and 15 wt-% while the chromium content ranges from 18-20 wt-%, with the balance being iron.